How to determine the sealing surface dimensions of a wafer butterfly valve
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Dear experts: Recently, when purchasing wafer-type linear butterfly valves, the standard number of the flanges to be used during installation was specified in the contract. However, the dimensions of the valve’s sealing surface provided by the valve manufacturer did not match those of the flanges; the valve’s sealing surface (the seat that extends out of the valve body and is used for sealing, with no gaskets required during installation) was smaller than the flange’s sealing surface, and the outer diameter of the valve’s sealing surface was only a few millimeters larger than the inner diameter of the flange. When requested to replace it, the manufacturer refused, stating that only the flange standards were specified in the contract and that wafer butterfly valves do not come with flanges; moreover, they were unable to provide the standards for the dimensions of the sealing surfaces used in their production. Has anyone encountered this situation? Are there specific standards for the sealing surfaces of wafer-mounted butterfly valves, or are they determined based on the flanges that accompany them? If anyone knows, please share some insights.
Butterfly valves are equipped with butterfly valve flanges, which, compared to the commonly used flat welding flanges, have a slightly smaller inner diameter and feature an internal groove to accommodate the installation of the butterfly valve.
What is the PN specification for this butterfly valve? What standard is used for the DN value? Isn’t it specified in the contract?
The current situation in the domestic market is as follows: for wafer butterfly valves with PN10-PN25 ratings, the same mold is used. The outer diameter of the wafer part (that is, the outer diameter of the protrusion on the RF flange) is designed for PN10 standards. Over the years, this has not had any impact on installation or use. And an important point is that the outer circumference of the sealing surface on the clamping parts (that is, the outer circumference of the protrusion on the RF flange) cannot be machined. The size of a casting is generally determined by its design, and the casting can only be of that size. Moreover, there is shrinkage during the casting process; therefore, the dimensions of valves from the same batch will vary. This is something that many laypeople do not understand. . In your case, you can try to address the issue by starting with the pipe flanges
Is the butterfly valve flange a standard component, and what is its corresponding standard number?
I once purchased a domestic wafer-type butterfly valve; although its price was relatively high, the sealing surface of the valve did match that of the accompanying flange. However, the price of this new manufacturer’s product is much lower, and the sealing surface of the wafer-type butterfly valve is significantly smaller, making it impossible to connect it to standard flanges. One can only use so-called \"butterfly valve flanges\", but even with these, the sealing surface is still much smaller than that of standard flanges. Can the sealing performance be guaranteed in such cases? “Is the “butterfly valve flange” a standard component, and are there any corresponding standard specifications?
For wafer butterfly valves, special butterfly valve flanges are required, which fit in like a snap. If butt-welded butterfly valves are paired with ordinary flanges, they can function fairly well for small diameters, but 90% of the time they leak for large diameters
The outer diameter, thickness, and bolt holes of the butterfly valve flange are the same as those of a regular flange; you can take a look at GB/T9119
You must be referring to flanged butterfly valves; the flanges used with wafer butterfly valves have different specifications from those of regular flanges.
It’s just that the inner diameter of the flange is slightly smaller, and there’s an additional inner groove on one side.